Diseases to Cannabis

One of the worst things imaginable to any grower is having a once-healthy vegetating or flowering marijuana plant fall victim to a preventable disease such as gray mold, deprivation illness or some other potentially fatal disease. However, there are several steps that can be taken to prevent these illnesses from occurring in the first place, as well as measures to bring disease-ridden plants back to health. There are literally hundreds of diseases, bacteria, viruses, molds, etc. known to cause harm to Cannabis. The following list, however, are the most common ones experienced by most North American growers.

Gray Mold:

Gray mold is a disease that, if left untreated or unnoticed, can kill an entire plant or even garden. It is most commonly seen during maturity in the flowering stage of the female Cannabis plant. Medical marijuana growers whose plants experience gray mold will first notice the tips of the leaves begin to turn a yellow-brown color, eventually wilting completely. This is followed by the pistils on the buds turning an unhealthy brown. This then advances to the tops of the nugs, where a fuzzy, gray mold begins to develop, reminiscent of strawberries that have been left out for a few days. If left untreated, this mold then spreads to become a grey-brown fuzzy slime that will then kill the entire crop.

To help prevent gray mold from occurring in the first place, make sure that your garden has humidity levels below 50% with plentiful ventilation. Like most other molds, this disease thrives in warm, moist climates with stagnant air. However, sometimes no matter how many precautions are taken, diseases still plague Cannabis plants. If you notice the beginning stages of gray mold occurring (yellowing of the tips of the leaves and even wilting), immediately remove the affected area by cutting off the discolored part of the leaf and add more ventilation, ensuring the humidity in the area is even lower. Unfortunately, once the buds are affected, your plant likely has little chance, but you can still remove the infested cola.

Deprivation Illness:

Deprivation illness is an easily preventable disease to marijuana that is caused simply by a lack of some necessary food or other nutrient. Needless to say, one way to ensure your hard-earned garden remains healthy is to continue providing it the necessary nutrients is requires, namely NPK (nitrogen, phosphate and potassium). If a plant is not receiving enough nitrogen, the lowest leaves will turn yellow, and if left untreated, fall off. If there is a shortage of phosphate, the leaves of the plant will turn a deep green, while not growing any larger in size and the lower leaves may yellow and wilt. The pH value is key to a plants health, especially in the case of potassium. If the soil is too acidic, the plant will not be able to receive enough calcium or potassium. In the case of a lack of potassium, the tips of the leaves will start to turn yellow, eventually spreading to the entire leaf, turning it a brown-yellow color. Shortages of iron, while rarely seen, cause the leaves to yellow and droop.

Mildew:

Mildew can mainly be prevented by controlling the growing environment of your garden. Different from most other moulds, mildew thrives in an environment with low humidity. While it is rarely seen in marijuana plants, it can cause the top of the plant to rot. The first sign of a mildew infestation is the leaves at the canopy yellowing and becoming weak. One of the most frustrating things about mildew is that it doesn’t usually rear its ugly head until the last week or two of the flowering period. Much to the utter dismay of growers who experience mildew, the entire top of the plant must be removed in order to ensure the entire plant does not become infected.

Pythium:

On the reverse end of the spectrum, pythium is a disease that affects the root system of marijuana plants. One of the most drastic outcomes of a pythium-infected plant is it falling over completely due to a lack of support at the base of the stem, where it has turned brown. Pythium causes the lowest part of the stem to rot, as well as the roots. This mould thrives in a moist, humid environment and can only be spread directly through water.

To prevent a pythium infestation, keep your soil or rockwool at a consistent temperature. When there is a large variation in the temperature of these, it creates a “window” for the pythium spores to manifest themselves on your plant. If your garden or plant has is showing signs of a pythium attack, chemicals may be used, but only in frugal amounts.

Comments

Guest | Jun 5, 2013

Last year I had mold that cost me dearly. I sprayed the mold with isopropyl alcohol. This kills the mold, but you have to catch it quickly. What can I do to prevent this from happening? Maybe a systemic? Dr. Earth? Please tell me what to use before it happens.

Guest | Mar 15, 2013

white powder =spider mites

Guest | Dec 9, 2012

I'm having a problem, the leaves are curling up as if it was too hot. Only the new growth does this. It looks like they are freeze dried. I live in hawaii so it's always hot but i never had this problem before. Any help would be appreciated.

Guest | Nov 25, 2012

I'm on bloom and my buds are dry??

Guest | Nov 10, 2012

the stems of the plant looks like the out side has been scrapped off

Guest | Jun 24, 2012

no white powder....but my plants look like they have white powder...more of a off white...other than that very healthy

Guest | May 3, 2012

i got a problem im a new grower in michigan and I found brown spots on my plants and its getting worse can some one help

Guest | Feb 13, 2012

my ladies look fine

Guest | Jan 30, 2012

my plants have a wite powder on the leaves help

Guest | Jan 30, 2012

all my plants leaves have wite powder on them whats rong

Guest | Sep 21, 2011

Please help! My plants are succumbing to a disease one by one. The first thing that happens is a number of fan leaves twist 180 degrees. Thus exposing the underside of the leaf. Then starting at the end of the branches and working downward the leaves turn yellow. And then finally the leaves at the end of the branch curl and turn brown (This looks exactly like fertilizer burn). If you know what this disease is and how to treat it please contact me

Guest | Jun 17, 2011

I have a brown rust looking substance on the center of the leaves. Anyone have any ideas what it is and if there is a cure?

Guest | Jun 17, 2011

I have a brown "rust" looking, possible fungus on the center of my plants leaves. Anyone have any idea what it is and how to cure/get rid of it?

Guest | Jun 2, 2011

spider mites suuuck been there try mighty wash its harmonicaly changed water

wow... wow I agree with mesterbimba that picture is truly a horrible and scary sight to see. I also have to agree with 818king between 68 and 72 is ideal temp for your little babies. But mainly that is just a scary sight and makes me worry.

That picture is seriously scaring me. It's hard to believe how vulnerable such a resilient plant can be. It goes to show why it is such an expensive product and how important marijuana's cultivators are in terms of their trade.

get lady bugs if u get spider mites you can buy some from a green thumb nursery they will take care of the bugs, mold rot sucks so try and make sure u keep the air moving and yr plants temps low 70s, if yr room is to hot for you its too hot for your plants